1. Field of the Invention
This invention relates generally to vacuum frames and, more particularly, is directed to a vacuum printing frame for reproduction purposes.
2. Description of the Prior Art
It is well known in the art to provide a vacuum frame for reproducing an original document or work of art utilizining a sensitized material.
In one known type of vacuum frame designed to expose and clear Dupont "Dylux" material, the apparatus includes a main frame having a recessed area within which are positioned a plurality of simultaneous instant start black light bulbs used for exposing the "Dylux" material. A glass frame is positioned above the bulbs and is secured to the top of the frame, and a blanket frame is hingedly secured to the main frame above the glass frame. Generally, the "Dylux" material and a film negative are positioned on the glass, and the blanket frame is then secured over the glass frame. A vacuum is then applied to the space between the blanket frame and glass frame so as to flatten the sensitized material and the film negative, and the black light bulbs are then simultaneously instantly started so as to develop the sensitized material in an exact copy of the film negative.
However, with such conventional vacuum frames, in order to change the black light bulbs positioned beneath the glass or to clean the bottom of the glass, either the glass must be removed, or alternatively, an access door is provided in the main frame to provide access to such area. This, of course, is troublesome, time-consuming and costly.
A photographic printing apparatus is also known from U.S. Pat. No. 1,742,372 to Taylor in which a plurality of incandescent lamps are located within a chamber in a cabinet of the apparatus, and two frames are pivotally connected to the apparatus above the lamps. In particular, one element or frame is hinged directly to the apparatus above the incandescent lamps and includes two parallel, spaced sheets of glass. A second frame or element which carries a sheet of rubber is pivotally connected to the first frame which carries the parallel, spaced sheets of glass. With this apparatus, sensitized objects to be printed on from negatives are placed on the top glass sheet and the upper frame is secured over the first frame, and a vacuum is created between the two frames such that the rubber sheet is drawn closely into contact with the negative and sensitized object. The patent discloses that the glass frame is hinged to the apparatus to enable ready access in case of necssity to the electric incandescent lamps positioned thereunder. There is no disclosure of maintaining the two frames open at different desired positions independent of each other.
U.S. Pat. No. 3,973,847 to Gygax et al. discloses the production of graphic patterns in which UV bulbs are positioned in a recessed portion of a housing, and a first frame carrying a transparent glass plate is pivotally connected to the housing by a hinge and a second frame carrying a rubber pressure mat is also pivotally connected to the housing above the glass frame and pivotally connected about the same hinge. A film negative and a metallic substrate, for example, are inserted between the glass plate and the rubber pressure mat above the UV bulbs to be exposed in the conventional manner. However, as with the Taylor Patent, there is no disclosure of any means for maintaining the lid and glass frame at desired pivoted positions independently of each other.
A "Dylux" proofer sold by The Douthitt Corporation of Detroit, Mich. is known similar to the types described in the above U.S. patents. In particular, the glass and blanket frames can be secured together and then raised together to clear the underside of the glass or for installing bulbs. A lock mechanism is provided for locking the frames at a single predetermined opened position. However, this unit suffers from the same deficiencies of the above U.S. patents.
Further, because of othe great combined weight of the glass and blanket frames, it is disadvantageous to lift the two frames together. In the first place, this is difficult to accomplish, and secondly, it is difficult to maintain the combined frames in an opened position.
Other patents which may be of interest are U.S. Pat. No. 2,594,920 to Halpern and U.S. Pat. No. 3,771,869 to Deihl et al.
It has also been known by the applicant to utilize a piston-cylinder arrangement in a vacuum frame setting, in which the glass frame is not pivotally secured to the apparatus, to maintain the lid containing the rubber mat at a desired pivoted position.